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Comparative Study Of Transition Elements Question Paper

Comparative Study Of Transition Elements

Course:Bachelor Of Science

Institution: Kenyatta University question papers

Exam Year:

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2008/2009
INSTITUTE OF OPEN LEARNING
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE
SCH 400: COMPARATIVE STUDY OF TRANSITION ELEMENTS
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DATE: THURSDAY 13TH AUGUST 2009 TIME: 8.00 A.M. – 10.00 A.M.
INSTRUCTIONS
Attempt ALL Questions.
1. Account for the following observations in the properties of transition metal elements
a) The highest oxidation state for the early transition metal elements Sc, Ti, V,
Cr, and Mn is the group number. On the other hand the highest oxidation
state for the later elements of the same period (Fe, Co, Ni, and Cu) is less than
the group number. (5 marks)
b) When AgNo3 solution is added to a solution of CrCl3 all the Cl- ions are
precipitated as AgCl, while only a third of the chlorides are precipitated
when the AgNO3 solution is added to a solution of WCl3 in water.
(5 marks)
c) The Lewis acidity of the pentahalides MX5 (M = V, Nb, Ta) decreases in the
order MF5 > MCl5 > MBr5 > Ml5. (3 marks)
d) The physical and chemical properties of Zr are similar to those of Hf but
differ significantly from those of Ti. (5 marks)
e) Chromium is able to form CrO2Cl2 but not CrCl6 and yet both contain Cr+6.
(3 marks)
Page 2 of 3
f) Tungsten can form WBr6 but chromium only forms CrBr4 even though they
are in the same group. (3 marks)
g) K2Cr2O7 is preferred to KMnO4 as a primary standard in volumetric analysis.
(3 marks)
Total = 27 marks
2. i) Draw the structure of each of the following species
a) Cr2O7
2-
b) VF5
c) TaCl5 (6 marks)
ii) Write a balanced net ionic equation for each of the following reactions.
a) A solution of Na2Cr2O7 turns from orange to yellow on addition of an
alkali to it.
b) Both acidic and alkaline MnO4
- solutions are decolorizing by
potassium iodide solutions. (6 marks)
Total 12 marks
3. State and explain the general variation trend of each of the following properties
across the first transition series of the Periodic Table.
a) Density
b) Ionization energy
c) Polarizing power of ions (6 marks)
Total = 14 marks
Page 3 of 3
4. a) Gandhi found a black material in a rock on their farm and suspected it to
contain MnO2. Briefly describe an experiment that he can carry out at the
Kenyatta University Inorganic chemistry laboratories to confirm that the
material contains manganese. Illustrate the possible reactions with balanced
equations. (7 marks)
b) Describe the sulphate process for the manufacture of pigment grade TiO2.
Explain why TiO2 has replaced white lead as a paint pigment base.
(10 marks)
Total = 17 marks

Comparative Study Of Transition Elements Question Paper

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